Diagram of the hydraulic suspension.

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Clogzz
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AndersDK

Joined: 11 Sep 2003
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Location: Denmark, Jylland East
Posted: Fri Sep 02, 2005 2:45 am Post subject: Overhauling a HC.

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The Height Corrector (HC) is the heart of hydropneumatic Citroen's automatic levelling suspension.

When your Citroen has problems achieving the correct ride height on start - and the linkages has been overhauled & greased, then the HC comes in as the main suspect for the problem.
A failing HC would almost always fail due to dirt, disturbing the moving of it's valve piston.
Sometimes the HC may leak from it's diagphragm, or even bulb out.
As always with Citroen hydraulic parts, mechanical wear is rarely seen.

The problem can be cured by overhauling the HC.
It's strongly recommanded to do a hydracleanse cure of the hydraulic system before overhauling the HC.
Simply to prevent your new/overhauled unit are gunked with dirt released by the Hydracleanse.

After removal of the HC, then immediately make an identification mark on the HC body for the ball-hooked end, as later you can't remember which end it goes. This marking should also show how the ball is fitted UP, related to the HC body.
Now clean the exterior of the HC in engine cleaner. Other detergents are not recommanded, as the rubber caps and diagphragms may be harmed.
Then remove the protective rubber caps, and further clean these down.



Referring to page 58 in the BX partslist or the above schematic, you can see how all bits are located. Note on this schematic the valve piston is still retained in the HC body.
Apart from the ball-hook, and mating hole in exterior protector cap, parts are identical at both ends, and fitting of parts are thus mirrored.
But note the ball hook end of piston rod has a longer protrusion, and longer thread.

Before disassembling, the ballhook must be removed from the piston rod.
First back off the nut opposite the ballhook end, ensuring it winds off easy.
Removing the ballhook may be a challenge, as most often the nut is stuck on the thread by rust and LockTite. Be careful if heating, as the rubber parts melts down if overheating.
I found clamping the hook in a vice, and then tapping on the nut with a tiny and sharp chisel did the trick, after heating to some 120'C. (heated air gun with tipped duct, lo setting on temp).
Any spanner seems to be defunct here, as the nut is too small for positive grip.

Start dismantling opposite to ball-hook end, noting how each bit is located/fitted during disassembly :
1) Unwind the small nut from piston rod and remove the steel dished washer.
2) Carefully prise off the diagphragm locator steel ring, by lubing the edge with LHM, then careful press out the ring from body in small steps, inserting a screwdriver, all the way 'round the circumference. Remove the ring from both ends of HC.
The rings may be very rusty.
3) Remove the diagphragm, the inner dished steel washer and the weak spring. Note how this spring fits against the dished washer.
4) The delicate thin steel shim is best removed by letting it drop off the piston rod. Then carefully remove the small circlip.
5) Free the diagphragm from HC body at ball hook end, then withdraw the piston rod with bits from HC body.
6) Now you possibly only have a return stud remaining as removable bit in the HC body. If fitted, then unwind & remove it. Do not remove the small brass return stud, which is a pressfit in the HC body.
7) Now disassemble the bits from the ballhook end the same way as above.

Thanks to Mike in West York for this important part :

The damper valve may clogg up, giving the impression that the HC is mechanically stuck during operation on car. It is very important that this damper valve is cleaned. This is seen as a series of small discs on the upper part of this picture. Shown is a DS HC with 6 (3 on each side to center) discs, later types have 10 discs.

Image

Looking straight at one end of the HC body, you will see the damper port, with a plug screwed into it to retain the damper discs. This plug needs a tool making to remove it – select a piece of steel rod (nail?) slightly smaller in diameter, and saw a slot in it that will go over the raised central part of the plug to unscrew it – it will not be too tight.
Carefully tap out the discs and spacers – all discs (10 if I recall correctly) are the same, but there is one larger spacer. Discs have minute central holes where dirt accumulates.

Cleaning :
All parts, except the rubber bits, are now brush-cleaned in petrol, and then dried.
They should either be lubed immediately with clean LHM, or stored in a bowl with clean LHM, as stain quickly builds up on the clean & dry steel bits.
The piston rod must be cleaned well in the fine grooves.
You can see which part of the piston rod is moving inside the HC body. If stain, even pitting, is found here, you must find a secondhand, or a new HC.
Outside this part of the piston rod, it's perfectly allright to clean/rub down any stain.

The HC body is first brushed/rubbed down for dirt, then progressively cleaned in petrol.
When the exterior is immaculate, then continue by cleaning all bores. Especially the very fine orifice off center, which - if blocked - is responsible for the diagpragm bulbing out.
Do not use any tooling that may mark the bores.
Blow clean the bores using an air line.
The rubber diagphragms are cleaned with LHM wetted clean rags, and left LHM wetted.

New parts :
If all parts are fine, there is no reason to replace as a precaution. But often the diagphragm retainer ring is a rusty mess, and the diagphragm may have split causing HC to leak. The outer protective caps are sometimes missing, or may have dried out and split.

Protector cap no hole : item 6 / 5 410 408
Protector cap w/ hole : item 7 / 5 410 407
Diagphragm rubber : item 11 / 5 410 732
Diagphragm retainer ring : item 8 / 5 410 406

Reassembly :
Ensure you have clean hands, then wipe all bits with a clean lintfree rag wetted with LHM during reassembly.
Starting opposite the ballhook end, the fitting is a reversal of ...
Use a tiny drop of LockTite on the threads when fitting ballhook/nut, then torque nuts, counter acting on one nut, sensible according to the size.

Refitting :
Before refitting on car, blank off the pipe ports. If dirt gets in while refitting the pipes, you're a looser.
A good dap of grease is applied to the ball hook.
Do the Citaerobics, then check the height setting.

Updated 09-10-04
2002 C5 2.0i AL4 230,000 km 76372389
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AndersDK
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Post by AndersDK »

Clogzz you are a hero 8)
Anders (DK) - '90 BX16Image
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Clogzz
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Post by Clogzz »

Thank you Anders ! :D

It wasn't difficult.
I have a little collection of those.
2002 C5 2.0i AL4 230,000 km 76372389
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